Stringed instrument designs are known to require adequate structural strength to accommodate the range of tension exerted from the string or groupings of strings required to reach the desired pitch. The instrument design also must be able to accommodate the increased tension of pulling on the strings, or otherwise activating the strings vibration pattern to produce sound. Stringed instrument designs should be able to withstand far greater tension than that required to reach pitch, in the event the strings are struck hard, get caught on something, or are tuned up temporarily to reach a higher pitch than that consistent with the design.
Some stringed instruments such as banjos and all bowed instruments from the smallest of violins to the largest of upright basses bear the string tension by attaching the strings to the back side of the instrument, rather than the top of the instrument. Often referred to as simply the “tailpiece” on bowed instruments or a “trapeze tailpiece” on guitars and basses, this method of string attachment minimizes downward pressure on the top of the instrument, and uses the lateral strength of the instrument's side structure to bear the load. Many stringed instruments such as acoustic guitar & bass utilize a design in which the strings penetrate the top of the instrument (sound board) and attach inside the guitar in a manner converting the tension into rotational pull.
Common understanding dictates that string tension on an acoustic bridge pulls in the direction of the strings. This results in a tendency to for the bridge area to pull in a rotational direction, since the strings are elevated off of the soundboard. This elevation converts the tension into torque, regardless of whether the strings are attached to the soundboard on top of the soundboard, or penetrate the soundboard and attach underneath the soundboard. The area behind the bridge pulls up into an arch, and the area in front of the bridge caves down and in. Substantial bracing is required to maintain an acceptable degree of straightness in the top over time. The bracing is oriented for required structural support and the negative impact of the bracing on vibrations of the top is implied and accepted.
One method U.S. Pat. No. 7,112,733 (Babicz) redirects the attachment point of the string end to a different place on the soundboard which moves the tension to the sides of the guitar where it can no longer drive the soundboard with the same inertia. A second method, U.S. Pat. No. 5,260,505 (Kendall) counteracts the rotational torque by adding pressure and mass in the opposite direction, arresting the vibration of the soundboard, and applying pressure to places that may or may not be designed to accept such pressure. Like Kendall, a third method, U.S. Pat. No. 7,462,767 (Swift) uses similar geometry as Kendall but applies the tension in the other direction to the neck block, rather than the heel block. Both Kendall and Swift anchor the torque redistribution to an area other than the instrument's soundboard, the area in which the device is intended to influence.
This system harnesses all of that tension to be utilized to the greatest degree as envisioned by the instrument designer. The designer is now free to brace soundboards for greater sonic manipulation, rather than compromising sonic properties for structural stability. U.S. Pat. No. 4,807,508 (Yairi) also utilizes all of the string tension on the soundboard, but splits the bridge into two sections. Aside from targeting certain sonic attributes, the benefit to Yairi was to reduce and/or eliminate failure of the glue joints holding the bridge and bridge plates to the soundboard. The string tension supports the glue joints instead of opposing them. This design spreads the torque across a larger area of the underside of the top, while making structural improvements in the way the torque is managed. The traditional relationship of the string anchors (ball ends) to the top, however, do not impart any negative torque into the soundboard, nor do they release torque from the assembly. Those skilled in the art have seen aging instruments with this technology which bulge in the area behind the bridge, from the inherent torque.
Current solutions have a negative impact on the sonic transfer to the soundboard, and therefore the sound and projection of the instrument into the space around it. Prior efforts to impart opposing torque forces through the use of an anchor point not located on the soundboard in the proximity of the bridge, work to reduce the energy transfer to the soundboard.
This invention is an improvement on what current attempts to manage and/or divert these forces. This system allows the full tension of the string to drive vibrations into the soundboard, which results in efficient generation of amplitude across a full frequency spectrum. This affords an optimal relationship between guitar design for tonal properties and structural stability.
This invention can also produce a stringed instrument vibrato unit that is self-equalizing. String tension and changes in pitch alter the zero position of traditional vibrato units, unless they are locked or stabilized by an outside force. The string tension itself can be harnessed so that variations in string tension are torque neutral, and only the intentional movement of the vibrato unit by the vibrato arm or other method would produce the change in pitch associated with vibrato units.